Current work is principally related to the study of hepatic apoprotein synthesis in vitro after treatment of rats with agents known to affect hepatic and circulating lipid levels. Amino acid incorporation into either HDL or LDL fractions has been shown to be elevated in livers from rats treated with diethylstilbestrol, estradiol, or fed low protein diets, but depressed in rats fed cholesterol; asparagine supplementation of cholesterol diets gave equivocal results; choline deficiency studies are still under way. Studies on the effects of dietary asparagine on hepatic lipidosis are also continuing in prepubertal rats in an attempt to explain the increased hypercholesteremia seen in young rats who demonstrate an apparent requirement for dietary asparagine.